The present invention relates to copying apparatus in general, and in particular to an electrostatic or xerographic copying apparatus.
Copying apparatus of the type in question is in worldwise use and comprises a transparent support, for example a glass plate or the like, onto which the material to be copied is placed face down. In many instances it is desired not to copy the entire original, but only to copy selected portions thereof. For this purpose it is known in the prior art to provide an arrangement in which only portions of the rotating copying drum of the apparatus are electrostatically charged, so that the electric charges of these selected portions correspond to the parts of the original that are to be copied so as to copy only portions of an original.
However, this approach requires rather substantial changes in existing copying apparatus which is of the type constructed for copying only the original in its entirety. A conversion for copying only increments of the original involves such far-reaching changes in the construction and operation of such apparatus, that it is very expensive.